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.TH CMP 1 "Jul 19, 2006"
.SH NAME
cmp \- compare two files
.SH SYNOPSIS
.LP
.nf
\fBcmp\fR [\fB-l\fR | \fB-s\fR] \fIfile1\fR \fIfile2\fR [\fIskip1\fR] [\fIskip2\fR]
.fi

.SH DESCRIPTION
.sp
.LP
The \fBcmp\fR utility compares two files. \fBcmp\fR writes no output if the
files are the same. Under default options, if they differ, it writes to
standard output the byte and line numbers at which the first difference
occurred. Bytes and lines are numbered beginning with 1. If one file is an
initial subsequence of the other, that fact is noted. \fIskip1\fR and
\fIskip2\fR are initial byte offsets into \fIfile1\fR and \fIfile2\fR
respectively, and can be either octal or decimal. A leading 0 denotes octal.
.SH OPTIONS
.sp
.LP
The following options are supported:
.sp
.ne 2
.na
\fB\fB-l\fR\fR
.ad
.RS 6n
Write the byte number (decimal) and the differing bytes (octal) for each
difference.
.RE

.sp
.ne 2
.na
\fB\fB-s\fR\fR
.ad
.RS 6n
Write nothing for differing files. Return exit status only.
.RE

.SH OPERANDS
.sp
.LP
The following operands are supported:
.sp
.ne 2
.na
\fB\fIfile1\fR\fR
.ad
.RS 9n
A path name of the first file to be compared. If \fIfile1\fR is \fB\(mi\fR, the
standard input is used.
.RE

.sp
.ne 2
.na
\fB\fIfile2\fR\fR
.ad
.RS 9n
A path name of the second file to be compared. If \fIfile2\fR is \fB\(mi\fR,
the standard input is used.
.RE

.sp
.LP
If both \fIfile1\fR and \fIfile2\fR refer to standard input or refer to the
same \fBFIFO\fR special, block special or character special file, an error
results.
.SH USAGE
.sp
.LP
See \fBlargefile\fR(7) for the description of the behavior of \fBcmp\fR when
encountering files greater than or equal to 2 Gbyte (2^31 bytes).
.SH EXAMPLES
.LP
\fBExample 1 \fRComparing Files Byte for Byte
.sp
.LP
The following example does a byte for byte comparison of \fIfile1\fR and
\fIfile2\fR:

.sp
.in +2
.nf
example% \fBcmp file1 file2 0 1024\fR
.fi
.in -2
.sp

.sp
.LP
It skips the first 1024 bytes in \fIfile2\fR before starting the comparison.

.SH ENVIRONMENT VARIABLES
.sp
.LP
See \fBenviron\fR(7) for descriptions of the following environment variables
that affect the execution of \fBcmp\fR: \fBLANG\fR, \fBLC_ALL\fR,
\fBLC_CTYPE\fR, \fBLC_MESSAGES\fR, and \fBNLSPATH\fR.
.SH EXIT STATUS
.sp
.LP
The following error values are returned:
.sp
.ne 2
.na
\fB\fB0\fR\fR
.ad
.RS 6n
The files are identical.
.RE

.sp
.ne 2
.na
\fB\fB1\fR\fR
.ad
.RS 6n
The files are different. This includes the case where one file is identical to
the first part of the other.
.RE

.sp
.ne 2
.na
\fB\fB>1\fR\fR
.ad
.RS 6n
An error occurred.
.RE

.SH ATTRIBUTES
.sp
.LP
See \fBattributes\fR(7) for descriptions of the following attributes:
.sp

.sp
.TS
box;
c | c
l | l .
ATTRIBUTE TYPE	ATTRIBUTE VALUE
_
CSI	Enabled
_
Interface Stability	Standard
.TE

.SH SEE ALSO
.sp
.LP
.BR comm (1),
.BR diff (1),
.BR attributes (7),
.BR environ (7),
.BR largefile (7),
.BR standards (7)
